One type of miniature individual switch includes a domed tripping member and an actuator that can be depressed to depress the middle of the tripping member. As the tripping member, or tripper moves down, it suddenly snaps down against a terminal to close the switch. The sudden snapping down creates a tactile feedback to a person depressing the actuator, to indicate that the switch has been closed. It is noted that the tripping member may be the form of a shallow pyramid instead of a continuously curved dome.
Electrical switches of this type are commonly mounted on circuit boards, together with many other components that are mounted on the circuit board. Since the tripper must repeatedly make and break contact with a terminal on the circuit board, it is desirable that the tripper lie in a substantially sealed environment to avoid corrosion and the presence of loose particles.
In accordance with one embodiment of the present invention, a tactile-feedback electrical switch is provided which accurately holds a tripper in a sealed environment on a circuit board using a minimum number parts. The switch includes an actuator molded of elastomeric material, and having a periphery with a lower sealing lip that surrounds the tripping member and which is pressed against the circuit board to seal thereagainst. The actuator has a center forming a rod and has a connecting portion connecting the rod to the periphery. The actuator forms a sealed cavity when its periphery is sealed to the circuit board. A cap which is fastened to the circuit board outside the actuator, presses down the sealing lip of the elastomeric actuator against the circuit board.
The tripper is formed with a plurality of arms that radiate from the middle of the tripper. The actuator has fingers that engage sides of the arms to accurately orient the tripper on the circuit board, and that retain the tripper prior to mounting on the circuit board. A skirt forming the periphery of the actuator lies in a press fit in the cap to keep them together prior to mounting on the circuit board. The inside of the actuator also has surfaces that press down against free outer ends of the tripper arms to press them against traces on the circuit board.
The rod formed at the center of the actuator includes a rod middle that merges with the connecting portion. The rod also has upper and lower rod parts that respectively project upward and downward from the rod middle. The rod upper part is exposed for receiving direct downward force to operate the switch. The rod lower part is tapered to have a small diameter lower face that lies substantially against the middle of the tripper.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.